This invention relates to a socket for a printed circuit board, into which an edge portion of the printed circuit board can be directly inserted, as a plug, to form a direct connector.
Recently, various direct connectors of low inserting force type have been developed to meet the demand for high-density fitting.
Generally, such a connector of low inserting force type has a plurality of spring contacts aligned in a hosing which is made of an insulating material and which constitutes a socket. The contact portions of the spring contacts are projected into an opening in order to insert a printed circuit board called a daughter board. The contact portions are arranged in two rows extending along the insertion opening. Between the rows of the contact portions there is provided a clearance for accommodating an edge portion of the printed circuit board. The contact portions of one row are arranged in offset fashion with respect to those of the other row, in the depth direction of the insertion opening, i.e. the direction in which the printed circuit board is to be inserted. When the printed circuit board is inserted, one surface of the edge portion contacts the contact portions of both rows, at a position close to the top of the edge portion, and the other surface contacts them at a position far therefrom.
When the edge portion of the printed circuit board is inserted into the gap between the contact rows and the printed circuit board is rotated, moving the contact rows away from each other, the contact portions of the spring contacts are displaced. Due to the spring force biasing the contact portions toward their initial positions, the contact portions reliably contact the wires, respectively, when arranged at the edge portion of the printed circuit board.
To reliably fix the printed circuit board to the housing, with the spring contacts maintained in the preferable contact with the printed circuit board, a latch mechanism is provided which holds the printed circuit board in its rotated position and secures the same to the housing.
Various types of latch mechanism have been developed.
A latch mechanism described in, for example, U.S. Pat. No. 4,986,765, comprises latch members shaped like leaf springs and formed of metal plates. These latch members hold a printed circuit board. They have spring portions set in the recesses made in the proximal portion of the housing, fitting portions projecting downward from the spring portions and inserted into an insertion opening of the proximal portion of the housing, and latch portions arranged above the spring portions. The latch portions have guide portions and cutouts. The guide portions abut on the edges of the printed circuit board to bias the spring portions outwards when the printed circuit board is rotated. The cutouts receives the side edges of the printed circuit board, thereby to hold the printed circuit board at a predetermined rotated position.
U.S. Pat. No. 5,161,995 discloses a latch mechanism comprising latch members which are shaped like leaf springs and formed of metal plates, like those described above. Each latch member has a fitting portion and a latch portion. The fitting portion is arranged at the lower side of spring portions, and the latch portion at the upper side thereof. The fitting portion has a pair of U-shaped fitting arms wound around a support pole positioned near the insertion opening of the printed circuit board. The fitting arms make an effect supporting a reaction force of the springs. Furthermore, the latch portions form guide surfaces for engaging with the edge of the printed circuit board and for biasing the spring portions outward when the printed circuit board is rotated, and engaging walls for engaging with one surface of the printed circuit board to prevent the printed circuit board from returning.
In either latch mechanism described above, the printed circuit board can easily be held or released, taking advantage of the characteristics of the metallic leaf springs.
Either type of the latch mechanism can be further improved in view of the fact that each latch members is formed of a metal plate.
While the printed circuit board is being fitted and rotated, the latch members are bent against the spring force, sliding along the guide portions or guide surfaces of the latch portions. A coated layer or an insulated substrate of the printed circuit board may therefore be damaged by the contact with the latch members or its sliding operation. Particularly, if the printed circuit board is relatively large or if more spring contacts are used because the printed circuit board has high density, the force these spring contacts generate will increase. Therefore, if the latch members are formed large enough to withstand the force, a greater force is required to bend the latch members. This increases the possibility that the printed circuit board is damaged.
At the time the latch members release the printed circuit board, it is desirable that the printed circuit board is made to jump and be reliably prevented from falling out of the socket due to the bias.